||The study "Microdelesi of Y Chromosome among NPFDB Infertility Clients" conducted by the Biomedical Unit, NFPDB is to identify infertility factors from a genetic aspect. Study samples were obtained from infertility patients referred to the Cytogenetic Laboratory, NPFDB from 2003 to 2010. A total of 100 blood samples of clients diagnosed as azoospermia (48), severe oligoasthenoteratozoospermia (24), oligozoospermia (15), severe oligozoospermia (6), Klinefelter Syndrome (3) and idiopathy (4) were performed Chromosome Analysis Tests to identify any abnormalities of the number and structure on the chromosome and subsequently Molecular Testing is performed to detect the microdeletion of the Y chromosome. Majority of ethnic groups involved in the study are Malays, which is 74 people (74%) followed by Chinese; nine (9) people (9%), Indians; seven (7) people (7%) and other ethnicities from Sabah and Sarawak as many as 10 people (10%) in the age range of 23 to 46 years.The chromosome analysis test results for the 100 samples were normal which is, 46, XY, no abnormalities in the structure or number of chromosomes were found. Results was found that 15 samples (15%) underwent Y chromosome microdeletion at the AZF locus in molecular test. From 15 samples, 10 samples were azoospermia, three (3) severe oligoasthenoteratozoospermia samples and two (2) oligozoospermia samples. Each sample experienced deletion at different locus and there were samples that experienced multiple deletion which involved deletion of more than one factor locus (AZF).The most common AZF factors found to experience deletion were AZFc (73.33%) followed by AZFb (53.33%), AZFd (40%) and AZFa (13.33%). In conclusion, it was found that genetic factors are one of the causes of infertility problems among clients came for subfertility treatment. Looking at the importance of undergoing genetic screening testing at an early stage, it is recommended that this test be tested for men diagnosed with azoospermia and severe oligozoospermia at the Subfertility Clinic, NPFDB. The information obtained has prognostic value and influences the medical therapy chosen to assist in the clinical management of the client and his descendant in the future.